1. Technical Field of the Invention
The present invention relates generally to radar technology, and, more particularly to a method and system for radar cross section self-test.
2. Description of Related Art
The survival techniques of aircraft in combat situations has undergone dramatic changes throughout the years. In the earlier days of aviation, survival of a combat aircraft was based upon speed. As avionics progressed, survival techniques progressed from speed to electronic capabilities. During World War I, visual detection in daylight did not exceed 15 miles. Even in the late 1930s, defenders were expected to listen and watch for attacking aircraft. By 1940, however, radar could spot incoming aircraft at a distance of more than 100 miles. Early detection gave defenders much more time to organize their air defenses and to intercept attacking planes, such as radar height-finding assisted anti-aircraft gunners. Primitive airborne radar sets were installed in night fighters in the later years of the war. Now, however, avionics have evolved to the point where one of the big keys to survival of an aircraft is in the stealthyness.
Since World War II, the radar game between attackers and defenders has determined who will control the skies. Radar domination allows firepower of air forces to bear against a foe or to deprive an enemy of this most valuable asset. Highly survivable aircraft contribute directly to achieving joint force objectives, and thus the ability to project power with efficient and effective air operations depends on controlling the radar contest.
Aircraft survivability depends on a complex mix of design features, performance, mission planning, and tactics. The effort to make aircraft harder to shoot down has consumed a large share of the resources dedicated to military aircraft design in the 20th century. Since the 1970s, the Department of Defense has focused on research, development, testing, and production of stealth aircraft, designed to blunt the power of defenders to detect them and thus defeat and/or destroy them.
Stealth technology minimizes aircraft signature in several ways but most notably by greatly reducing its radar signature. Low-Observable (LO) aircraft such as the first operational stealth aircraft, the F-117 and the B-2, demonstrated the feasibility of LO aircraft and their importance to more effective air operations. Like all combat aircraft, they have limitations that must be recognized to ensure proper employment.
An aircraft on a mission may become proximate to anti-aircraft fire or fragments which can strike the aircraft. Conventionally, such a fragment typically doesn""t do a great deal of damage however, the fragment is capable of disfiguring the aircraft to actually compromise the aircraft by increasing the radar signature. In order to maintain the stealthyness, the aircraft must be repaired between missions. Unfortunately, the repairs may appear sound upon visual inspection however, the repair work may still be apparent on radar.
Currently one method for testing the RCS of an aircraft involves the building of a model of an aircraft and hoisting it up on a big radar pole. The aircraft is then shot with radar and the radar signature or the radar cross section (RCS) is measured. The aircraft signature can also include, for example, infra-red signatures, visual signatures, or acoustic signatures. RCS measurements are customarily made on radar cross section ranges or labs. Such ranges basically consist of a test radar that sends radar signals to a remotely positioned test target and receives and measures any returned radar echo, as may be reflected from the object. Typically the test target is supported upon or suspended from an RCS test mount.
When operating LO aircraft, one doesn""t always know if the RCS is as low as that which it was designed. Many actions and events in the aircraft""s life can affect is RCS, e.g., maintenance, battle damage, erosion. Scattering centers may be produced on the LO aircraft by patches of dirt, production defects, exterior damage, or incompletely closed access doors. Such conditions may go unnoticed by maintenance personnel and pilots in the field. Furthermore, repairs and production defects may leave imperfections that may not be detected by visual inspections. As a result, the aircraft may be vulnerable to radar detection. Unless the aircraft is brought to an ISAR test range, these conditions will often remain undetected.
The present invention achieves technological advances as a system and method for self-determining a radar signature of a target in which the target has a radar transceiver. The target is positioned at a predetermined distance from a reflective surface, such a flat metal surface, and the transceiver is used to transmit an energy signal toward the reflective surface. The reflective surface is positioned to reflect the energy signal back toward the target. Energy reaching the target reflects from component parts of the target back toward the reflective surface which reflects the energy back toward the target again where the transceiver receives the returned energy and calculates a radar signature indicative of the returned energy signal.